WASHINGTON – The chairman of the United States’ National Transportation Safety Board (NTSB) said it was “very, very fortunate” that a tragedy did not materialise after a cabin panel blew out on an Alaska Airlines Boeing 737 Max 9 on Jan 5, which forced the aircraft to make an emergency landing.

NTSB chair Jennifer Homendy said the two seats next to the portion of fuselage that blew out were unoccupied.

“We are very, very fortunate here that this didn’t end up in something more tragic,” she added. Parts of the seat next to the fuselage, including the head rest, were missing.

Investigators will look at maintenance records, the pressurisation system and the door components, she said.

“We’ll go where the investigation takes us,” she said, asking for the public’s help in recovering the missing door plug, which is believed to be in a suburb west of Portland.

A piece of fuselage tore off the left side of the jet as it climbed following takeoff from Portland, Oregon, en route to Ontario, California, forcing pilots to turn back and land safely with all 171 passengers and six crew on board.

The Federal Aviation Administration (FAA) on Jan 6 ordered certain Max 9 aircraft grounded temporarily for inspections before returning to flight. The move, affecting 171 planes worldwide, followed decisions by Alaska Air and United Airlines Holdings, the two biggest Max 9 operators, to ground dozens of jets in their fleets.  

Both airlines are the only US carriers using the Max 9, according to aviation data provider Cirium. Alaska cancelled 160 flights on Jan 6, or 20 per cent of scheduled trips, while United cancelled 115 flights or 4 per cent of departures.

Outside the US, Turkish Airlines has withdrawn its five Boeing 737 Max 9 aircraft from service for inspection, while India’s aviation regulator has ordered an inspection of all Boeing 737 Max 8 aircraft owned by domestic operators.

None of India’s air operators have the Boeing 737 Max 9 model in their fleets, but the country’s Directorate-General of Civil Aviation (DGCA) has directed an immediate one-time inspection of emergency exits on all Max 8 aircraft currently operating as part of their fleet.

Panamanian carrier Copa Airlines said it had temporarily grounded 21 Max 9 aircraft and said it “expects to return these aircraft safely and reliably to the flight schedule within the next 24 hours”. It added that some delays and cancellations are expected.

In response to queries from The Straits Times, a Singapore Airlines spokesperson said SIA does not operate any Max 9 aircraft, and is “not affected” by the FAA directive to ground Max 9 aircraft for inspection.

A look at ‘plugged’ doors

The Boeing 737 Max 9 is built with modular cutouts in the frame that can house additional emergency exits for high-density configurations. Some airlines order planes with the doors installed to maximise the number of seats, while others, like Flight 1282 operator Alaska Airlines, do not require the extra exits and have the holes permanently plugged up.

From the inside, a plug is indistinguishable from the sidewall on the aircraft, while on the outside, an outline of the opening can be seen.

This reflects a design feature which has been in use for many years, since the mid-2000s, which suggests that investigators are likely to zero in on issues in the manufacturing process rather than a design flaw.

“This has all the earmarks of a manufacturing deficiency, a quality escape from Boeing,” said aviation safety expert Jeff Guzzetti, the FAA’s former accident investigation chief.

“We can’t help to not look at this recent event in the context of all the problems that Boeing has had with manufacturing quality deficiencies.”

Investigators will have to look into how the doors are plugged and why they exist if they can come open, said Mr Richard Healing, a former member of the NTSB.

“It’s going to be serious engineering work and maintenance work, and certainly an opportunity for NTSB to dig in on this, and the FAA as well,” said Mr Healing, the chief executive of consultancy Air Safety Engineering. “My sense is that this is just the beginning of something.”

‘The side of the plane is gone’

A passenger on the Jan 5 flight, Vi Nguyen of Portland, said that she woke up to a loud sound during the flight. “I open my eyes and the first thing I see is the oxygen mask right in front of me,” said Ms Nguyen, 22.

“And I look to left and the wall of the side of the plane is gone.”

“The first I thought was, ‘I’m going to die,’” she added.

Another passenger, Ms Elizabeth Le, said she looked up to see a large hole in the wall of the plane about two or three rows away from her after hearing “an extremely loud pop”. Ms Le said that no one was sitting in the window seat next to the hole in the wall, but a teenage boy and his mother were in the middle and aisle seats.

Flight attendants helped them to move to the other side of the plane a few minutes later, she said, adding that the boy appeared to have lost his shirt, and his skin looked red and irritated.

“It was honestly terrifying,” said Ms Le, 20. “I almost broke down, but I realised I needed to remain calm.”

Boeing has struggled in recent years with technical and quality control issues related to its 737 Max models.

In December 2023, the US aviation giant told airlines that Max aircraft should be inspected for loose hardware on plane rudder control systems, after an international operator discovered a bolt with a missing nut while performing routine maintenance.

Boeing’s 737 Max models were grounded worldwide following two Max 8 crashes in 2018 and 2019 that killed 346 people in total.

The FAA approved the planes’ return to service only after the company made changes to its flight control system. REUTERS, BLOOMBERG, NYTIMES, AFP